let obj = {
  name: "FreeCodeCamp",
  review: "Awesome",
};
Object.freeze(obj); // 冻结以后 无法再从中添加，更新或删除属性。更改对象的任何尝试都会被拒绝，不会出错。
obj.review = "bad"; // will be ignored. Mutation not allowed
obj.newProp = "Test"; // will be ignored. Mutation not allowed
console.log(obj);
// { name: "FreeCodeCamp", review:"Awesome"}
